Flashcards in Water Balance Deck (69):
Dehydration is a deficit in body fluids caused by what 6 things?
Vomiting, diarrhoea, excessive sweating, low water intake, drainage from burns, damage to thirst mechanism
What are the 9 things that are important about water in the body?
Universal solvent, chemical reactions occur in water, found as major component of plasma and cells, lubricant of joints and organs.highh ability to absorb and retain heat - stays in liquid state over broad range of temperature 0-100 degrees, large amount of heat required to increase its temperature - stabilises body temperature, sweating carries a lot of heat away from the body.
How many litres is our total body water?
How do we get water into the body?
Drinks (1500ml) food (750ml) water of metabolism (250ml)
How do we get rid of water from the body?
Urine (1500ml) stools (100ml) sweats (200ml) respiratory loss (700ml)
What is the body composition of an average 70kg man?
Where is the water in the human body?
25L intracellular fluid, 12L extracellular fluid, 3L plasma
What is simple diffusion?
Movement from an area of high concentration to an area of low concentration through a semi - permeable membrane
What allows substances to move in and out of cells
How does an increase in temperature affect the rate of diffusion?
Increase motion of particles
How does molecular weight affect the rate of diffusion?
Larger molecules move slower
How does steepness of concentration gradient affect rate of diffusion?
Increased difference means increased rate
How does membrane surface area affect rate of diffusion?
Increase in area means increase in rate
How does membrane permeability affect rate of diffusion?
Increase in permeability means increase in rate
What is osmosis?
The diffusion of water from a lower to a higher concentration
Define a solution
A homogenous mixture of one or more dissimilar substances usually a liquid (solvent) and a solute (electrolyte - dissolved particle)
Name 3 types of solution that are based on size
Aqueous solutions are made up of?
Small molecules which dissolve
Ionic compounds which dissociate
Electrolytes are soluble inorganic molecules whose ions conduct electricity in solution
Colloids are made up of
Proteins or other large molecules as solute
Suspensions are made up of
Even larger molecules than colloid solutions
Particles settle if undisturbed
What is the osmotic pressure?
The force (thrust) of water movement into the higher concentration solution
What and concentration solutions be measured as?
G/L - weight or volume
1 mole = number of atoms/molecules present in a sample equal to the molecular weight in grams
What is osmolarity?
Number of osmoles/L solution
The osmotic concentration of the body fluids have a great effect on what?
The effect of osmolarity is dependant on what rather than what?
Number of particles dissolved rather than the weigh of the molecule
Osmotic concentration is expressed in what?
Osmoles/L or Kg
Number if osmoles/kg of H20
Number of osmoles/L of H20
Name the 3 tonicity's that a cell can be
If a cell is in an isotonic solution
Concentration of electrolytes outside the cell is equal to that inside the cell
No water movement
No change in cell shape
A cell in a hypotonic solution
Has low concentration of salutes that do not cross the membrane, high water content
Cells absorb water and swell, if solution is to dilute cell may burst (lysis)
Cell in a hypertonic solution
Low water concentration and high concentration of salutes that do not cross the membrane
Water moves to try and balance water/ion concentration
Cells in this solution would lose water and shrivel up
What happens when body water is low?
Baroreceptors and osmoreceptors send messages to the thirst centre in the hypothalamus. This releases ADH, we get thirst and a dry mouth and so drink
List 4 treatments for dehydration
5% glucose solution
What can over hydration cause?
Any fluid movement results in what?
Change in osmotic pressure, electrolytes on one side of the membrane therefore cell will change size
Water will always follow what?
What do we call substances that are dissolved in solutions?
Which of the following is he most concentrated solution?
A - 0.9% saline
B - 100g/L saline
C - 9mg/100mls saline
B = 10%
C = 0.009%
What are the 5 functions of water in the body
Chemical reactions occur in water
Major component of plasma and cells
Lubricant of joints and organs
Helps control body temperature
What is fluid intake and output controlled by?
Kidneys, anti diuretic hormone
Describe the process of water balance and ADH
Sensory nerve cells in the hypothalamus detect changes in the osmotic pressure of the blood. Nerve impulses from the osmoreceptors stimulate the posterior pituitary to release ADH. Raised osmotic pressure =blood more concentrated, ADH output is increased, increasing water reabsorption in the kidneys - negative feedback mechanism.
Define osmotic pressure
Force of water movement into the higher concentration solution.
What does extra cellular fluid In the interstitial spaces mainly consist of?
Blood, plasma, lymph and CSF fluid.
What is the role of extra cellular fluid?
Give 3 examples of extracellular fluid
Synovial fluid, pericardial fluid (around the heart), pleural fluid (around the lungs)
What does interstitial fluid do?
Bathes all the cells of the body except the outer layers of the skin, medium through which substances pass from blood to body cells and vice versa.
What would a fall in blood potassium cause?
Muscle weakness and cardia arrhythmia
Name a difference between intracellular and extracellular fluid.
Intracellular fluid has a lot less sodium
What substances are found inside the cell in higher amounts?
ATP, protein and potassium
Substances that are dissolved in solutions
Mixture of 2 or more dissimilar substances, usually a liquid into which a solid is dissolved
Osmotic pressure of substance expressed as osmoles of substance per kg of water
Osmotic pressure of a substance expressed in terms of osmoles of substance per L of water
Ability of a solution to affect the cell
A charged molecule, eg calcium, sodium, potassium
What is calcium involved in
Bones, muscle contractions, nerve excitability
What is sodium involved in
Action potential, osmotic pressure, nerve conduction
What is potassium involved in
Nerve cell returning to resting state
What is hydrogen involved in
What is chloride involved in
Transported with sodium and potassium
What is bicarbonate involved in
Acid balance - counter acts hydrogen
Give 2 examples of passive transport
What does active transport require
The transfer of what would require active transport?
Sodium, chloride, glucose
Which for, of transport moves up the concentration gradient and requires energy?
What happens during facilitated diffusion?
Molecules are too big to diffuse across the membrane, bind to receptors in carrier proteins which causes molecule to change shape, molecule drops off carrier protein and ends up inside the cell,
Carrier proteins are always....